Heat-sealed laminated packaging structures are regularly employed to contain numerous materials. It is common for laminated bags to be used to contain surgical implements, including sutures, scalpels and the like. It is also becoming increasingly popular to employ heat-sealed laminated bag constructions as a replacement for cans in holding foodstuffs for extended periods of time.
A problem which is common to these different uses for laminated packaging structures is the sterilization of the materials contained within the constructions. Prior known laminated packaging constructions for foodstuffs provided a heat seal which was sufficiently strong to hold the foodstuffs contained therein, even under the conditions of retorting to sterilize the foodstuffs after packaging thereof, which retorting typically occurs at temperatures in the range of 250.degree. F. (121.degree. C.). However, such bonds typically have peel strengths in the range of about 14 to 18 pounds per inch (2500.4 to 3204.8 grams per centimeter), which is far too high to permit peeling of the seal by hand.
Peelable heat seals have been obtained in the packaging of medical supplies, such as sutures and the like. These heat seals have seal strengths of about 2 to 3 pounds per inch (357.2 to 535.8 grams per centimeter) as sealed. However, these seals cannot withstand the retort sterilzation process, resulting in failure of the seals. Since such containers cannot be effectively sterilized after sealing thereof, it is necessary that such medical supply material be sealed within their packages under sterile conditions, such as in the presence of a sterile gas.
It is desirable, therefore, to produce a laminated packaging construction which provides a heat seal having the ability to withstand retorting to enable sterilization of a package after sealing thereof and which is peelable by hand after retorting to enable opening of the package without resorting to external opening means, such as cutting apparatus.